1. Field of the Invention
The present invention relates to fuel transfer from a plurality of fuel tanks to the engine of a vehicle, and more particularly, to a method and apparatus for maintaining substantially equivalent fuel levels within the plurality of fuel tanks.
2. Description of the Related Art
Vehicles such as, for example, heavy and medium duty trucks commonly employ a dual tank configuration providing a large fuel capacity. The two tanks are positioned on opposing sides of the truck. Such dual tank configurations are troublesome to fill. Either two fuel dispensers must be used (one on either side of the truck), or the truck must be turned around so that both fuel tanks may be filled using a single fuel dispenser.
As is known in the art of internal combustion powered vehicles, fuel pumps remove more fuel from fuel tanks than is utilized in the engine so as to cool the fuel injector pump. The surplus fuel which is not used by the engine is constantly returned to the fuel tank. In the dual tank configurations currently utilized with heavy and medium duty trucks, fuel is drawn from and returned to both fuel tanks simultaneously. These systems do not draw fuel evenly from both tanks nor do they return fuel evenly to both tanks. Uneven fuel draw and return can be attributed to many factors affecting fluid flow, including pressure differentials and physical attributes of the fluid distribution system including, but not limited to partial blockage of distribution piping. Spillage may occur if fuel is drawn primarily from one of the two tanks and fuel is returned primarily to the other of the two tanks.
Roads and parking areas are generally formed with a crowned configuration leading to one of the two fuel tanks being lower relative to the other. Fuel is more easily drawn from the higher tank and consequently the lower tank has less fuel drawn from it. This exacerbates the problem of uneven fuel draw and the consequent spillage which can occur.
Uneven fuel draw and return additionally causes balance problems when one of the two fuel tanks contains significantly more fuel than the other. Hydrocarbon fuel typically weighs approximately 6 lbs. per gallon and the fuel tanks in question generally have a capacity of approximately 100 gallons. The substantial weight differential caused by an uneven amount of fuel in the two tanks can cause maintenance and other problems for the truck operator including, for example, uneven tire wear. An additional problem associated with the dual tank configuration occurs when one of the two tanks is emptied and air is drawn into the engine from the fuel supply line connected to the empty tank. When air is drawn into the engine, engine stall is experienced and restarting the engine is problematic.
The present invention is directed to improve upon the aforementioned fuel storage and distribution systems for heavy and medium duty trucks wherein it is desired to utilize a dual tank configuration in which the fuel levels in both tanks remain substantially equal. The present invention provides an electric transfer pump configured to be in fluid communication with both fuel tanks. Fluid level sensors measure the fluid level in both fuel tanks and are communicatively connected to the electric transfer pump. When the fluid level in one of the tanks reaches a predetermined lower level than in the other tank, the electric transfer pump distributes fuel from the tank having the greater fuel volume to the other tank. The electric transfer pump may be configured so that fuel can be transferred in either direction between the two fuel tanks.
In one form of the current invention, the first of the two fuel tanks is in direct fluid communication with the engine whereby fuel is supplied to the engine from the first tank and excess fuel returning from the engine is returned to the first tank. Fuel level sensors are operatively connected to both fuel tanks. Fluid level measurements from the two fuel level sensors are communicated to an electric transfer pump. The electric transfer pump includes a computational/control device such as a microprocessor or a programmable logic controller which evaluates the two fuel level signals and determines whether fuel should be transferred from the second fuel tank to the first fuel tank. Fuel is transferred when the fuel level in the first fuel tank reaches a predetermined lower level than the fuel level in the second fuel tank.
The computational/control device can be contained within the electric transfer pump as described above or may be placed in the standard truck circuit board which controls other truck electric operations. The electric transfer pump may, for example, take the form of a pulse width modulated solenoid pump or a DC motor driven positive displacement pump.
An advantage of the present invention is the ability to prevent fuel spillage in a dual fuel tank configuration by eliminating the possibility that more fuel is returned to a fuel tank than is taken from the fuel tank.
Another advantage of the present invention is the ability to maintain substantially equal fuel volumes within a dual tank configuration and thus eliminate balance problems associated with unequal fuel volumes.
A further advantage of the present invention is the ability to eliminate engine stall occurring as a result of air being drawn from an empty fuel tank.
Yet another advantage of the present invention is the ability to utilize the electric transfer pump to transfer fuel provided to one fuel tank to the other fuel tank while fueling so that the problems associated with filling a pair of fuel tanks on opposing sides of a vehicle are not experienced.